title: Distinct galactose phosphoenolpyruvate-dependent phosphotransferase system in Streptococcus lactis.
abstract: Lactose-negative (Lac-) mutants were isolated from a variant of Streptococcus lactis C2 in which the lactose plasmid had become integrated into the chromosome. These mutants retained their parental growth characteristics on galactose (Lac- Gal+). This is in contrast to the Lac- variants obtained when the lactose plasmid is lost from S. lactis, which results in a slower growth rate on galactose (Lac- Gal+). The Lac- Gal+ mutants were defective in [14C]thiomethyl-beta-D-galactopyranoside accumulation, suggesting a defect in the lactose phosphoenolpyruvate-dependent phosphotransferase system, but still possessed the ability to form galactose-1-phosphate and galactose-6-phosphate from galactose in a ratio similar to that observed from the parental strain. The Lac- Gald variant formed only galactose-1-phosphate. The results imply that galactose is not translocated via the lactose phosphoenolpyruvate-dependent phosphotransferase system, but rather by a specific galactose phosphoenolpyruvate-dependent phosphotransferase system for which the genetic locus is also found on the lactose plasmid in S. lactis.
mesh_terms: D004187:Disaccharides / Q000378:metabolism; D005690:Galactose / Q000378:metabolism*; D005695:Galactosephosphates / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006026:Glycoside Hydrolases; D013294:Lactococcus lactis / Q000201:enzymology*; D007785:Lactose / Q000378:metabolism; D008756:Methylgalactosides / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D013862:Thiogalactosides / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D004187:Disaccharides; D005695:Galactosephosphates; D008756:Methylgalactosides; D013862:Thiogalactosides; C009468:thiomethylgalactoside; C005608:lactobionic acid; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D006026:Glycoside Hydrolases; D001616:beta-Galactosidase; C022361:6-phospho-beta-galactosidase; D005947:Glucose; D007785:Lactose; D005690:Galactose